Ok next set of questions.I bought 2 * continues rotation servo motors for drive of a buggy. When testing i found they do not run at the same speed. I tried software and mechanical to calibrate but it did not work. They were cheap servo.So can the pi control stepper motors ? if so what power can they controlI have 1 or 2 servo motors when i use they seem to crash Robopi out as in i have to reboot completely. Why? is there a power overload ?currently using a ultrasonic detector but they are prone to angle and material type is there a radar system for it ? My current project is just a 3 wheel buggy but it must be able ( in time ) to map its area.Any ideas or help would be great

DarkGoat wrote:Ok next set of questions.I bought 2 * continues rotation servo motors for drive of a buggy. When testing i found they do not run at the same speed. I tried software and mechanical to calibrate but it did not work. They were cheap servo.

It should be possible to calibrate them with software, as long as you calibrate it when it has the final load on it - ie run it on the ground.

DarkGoat wrote:So can the pi control stepper motors ? if so what power can they control

I'd stick with continous rotation servos or gear motors for robots.

Google "raspberry pi controlling stepper motor" for some results on how to control stepper motors with a Raspberry Pi.

I'll see if I can add some stepper motor control options to RoboPi in a future firmware release.

DarkGoat wrote:I have 1 or 2 servo motors when i use they seem to crash Robopi out as in i have to reboot completely. Why? is there a power overload ?

Because they draw too much power from the Pi's 5V which was never designed to power motors.

RoboPi has screw terminals for a separate power pack for servos/motors - just move the SV2&SV3 the Vbat settings and add a battery pack for the motors.

Simplest is 4xAA's (alkaline) or 5xAA NimH connected to the screw terminals. There is a polarity protection diode that will drop 0.7V, and make sure that you do not exceed your servo's max voltage.

DarkGoat wrote:currently using a ultrasonic detector but they are prone to angle and material type

Yes.

DarkGoat wrote: is there a radar system for it ?

Google for IR and/or ultrasonic radar/lidar code, it is pretty easy. Use a standard servo to scan 180's, and remember, ultrasonic sensors usually have a 10'-15' beam width.

I wrote an IR based radar for the Propeller a few years ago, but I have no idea where the code is now.

What IR sensor did you use for the ir radar ?Was it at ground level or just above ?Would ultra sonic do the same job or is IR better ?Also you were right about the servo motors Iv gone back to 2 wheel drive so far it close enough for what i want.

I am trying to setup 3 digital outputs from the robopi however the best output voltage i can get is 3.5v. This is enough to work but as i change the 3 output values they dont work.ie. step 1 set output 16 ,1 set output 15 ,1 set output 14,1This may work. next statement may read set output 16,1 set output 15.0 set output 14.1This is where things go wrong voltages vary on outputs from .1V to 1.4V. I cannot seem to control it.Note the above is not the full software the code is written correctly with no errors. Its the outputs that are wrong.Maybe I have wired incorrectly but i can not find any solution or wiring diagram on the internet.

It sounds like you are trying to pull more current from RoboPi than the P8X32A can supply.

Note that you should pull no more than 10mA per pin (ok, you can pull 20mA from one or two pins usually)

For example, if you are trying to drive relay coils directly, or motors, you WILL have problems.

DarkGoat wrote:I am trying to setup 3 digital outputs from the robopi however the best output voltage i can get is 3.5v. This is enough to work but as i change the 3 output values they dont work.ie. step 1 set output 16 ,1 set output 15 ,1 set output 14,1This may work. next statement may read set output 16,1 set output 15.0 set output 14.1This is where things go wrong voltages vary on outputs from .1V to 1.4V. I cannot seem to control it.Note the above is not the full software the code is written correctly with no errors. Its the outputs that are wrong.Maybe I have wired incorrectly but i can not find any solution or wiring diagram on the internet.